{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T05:00:55Z","timestamp":1787029255239,"version":"build-2736575974"},"reference-count":50,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T00:00:00Z","timestamp":1769990400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["UIDB\/50006\/2020"],"award-info":[{"award-number":["UIDB\/50006\/2020"]}]},{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["UIDP\/50006\/2020"],"award-info":[{"award-number":["UIDP\/50006\/2020"]}]},{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["UIDB\/05937\/2020"],"award-info":[{"award-number":["UIDB\/05937\/2020"]}]},{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["UIDP\/05937\/2020"],"award-info":[{"award-number":["UIDP\/05937\/2020"]}]},{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["UID\/50027"],"award-info":[{"award-number":["UID\/50027"]}]},{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["UIDP\/04378\/2020"],"award-info":[{"award-number":["UIDP\/04378\/2020"]}]},{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["UIDB\/04378\/2020"],"award-info":[{"award-number":["UIDB\/04378\/2020"]}]},{"name":"the CESPU-Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio, under the SALMYTH_GI2-CESPU_2022 project","award":["LA\/P\/0140\/2020"],"award-info":[{"award-number":["LA\/P\/0140\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pathogens"],"abstract":"<jats:p>Antimicrobial Resistance (AMR) is a critical public health challenge requiring a coordinated One Health approach. Escherichia coli is a key indicator of AMR and fecal contamination, as well as a zoonotic pathogen transmissible from animals to humans, often through contaminated products like meat and eggs. This study assessed the presence of antibiotic-resistant E. coli and associated resistance genes in 248 cloacal\/eggshell samples collected from four autochthonous Portuguese laying hen breeds (Preta Lusit\u00e2nica, Amarela, Branca, and Pedr\u00eas Portuguesa) raised under low antibiotic exposure. A total of 81 E. coli isolates were analyzed for phenotypic antibiotic susceptibility (EUCAST\/CLSI) and genotypic resistance, using PCR. Resistance to at least one antibiotic was observed in 98.0% of the isolates. Gentamicin resistance was particularly high (97.1% cloacal; 95.7% eggshell isolates), followed by tetracycline (31.0% cloacal; 41.0% eggshell) and ampicillin (14.0% cloacal; 24.0% eggshell). Multidrug resistance (MDR) was observed in 14.3% of cloacal and 17.4% of eggshell isolates. Notably, no resistance was found against critically important antibiotics. The most prevalent resistance genes were sul2 (45.0% cloacal; 48.0% eggshell) and blaTEM (45.0% cloacal; 36.0% eggshell). Detection of resistant and MDR E. coli in low input systems suggests environmental acquisition, with chickens as reservoirs, highlighting the need for One Health surveillance.<\/jats:p>","DOI":"10.3390\/pathogens15020163","type":"journal-article","created":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T15:38:12Z","timestamp":1770046692000},"page":"163","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Silent Reservoirs: Antibiotic-Resistant Escherichia coli in Autochtonous Portuguese Laying Hens"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-2327-5527","authenticated-orcid":false,"given":"Rita","family":"Jesus","sequence":"first","affiliation":[{"name":"University Institute of Health Sciences, Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio (IUCS-CESPU), Avenida Central de Gandra 1317, 4585-116 Paredes, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0854-2771","authenticated-orcid":false,"given":"Sandra","family":"Quinteira","sequence":"additional","affiliation":[{"name":"UCIBIO\u2014Applied Molecular Biosciences Unit, University Institute of Health Sciences (1H-TOXRUN, IUCS-CESPU), Avenida Central de Gandra 1317, 4585-116 Paredes, Portugal"},{"name":"CIBIO\/InBIO\u2014Research Center in Biodiversity and Genetic Resources\/Research Network in Biodiversity and Biodiversity and Evolutionary Biology, Associated Laboratory, University of Porto, Campus de Vair\u00e3o, Rua Padre Armando Quintas 7, 4485-661 Vair\u00e3o, Portugal"},{"name":"BIOPOLIS Program in Genomics, Biodiversity and Land Planning, Campus de Vair\u00e3o, Rua Padre Armando Quintas 7, 4485-661 Vair\u00e3o, Portugal"},{"name":"Department of Biology, Faculty of Sciences, University of Porto, Rua do Campo Alegre s\/n, 4169-007 Porto, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Virg\u00ednia","family":"Ribeiro","sequence":"additional","affiliation":[{"name":"ANGRA\u2014Associa\u00e7\u00e3o Nacional dos Criadores de Galinhas de Ra\u00e7as Aut\u00f3ctones, 4775-060 Barcelos, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8719-1281","authenticated-orcid":false,"given":"Rui","family":"Dantas","sequence":"additional","affiliation":[{"name":"University Institute of Health Sciences, Cooperativa de Ensino Superior Polit\u00e9cnico e Universit\u00e1rio (IUCS-CESPU), Avenida Central de Gandra 1317, 4585-116 Paredes, Portugal"},{"name":"FERA\u2014Federa\u00e7\u00e3o Nacional das Associa\u00e7\u00f5es de Ra\u00e7as Aut\u00f3ctones, 4800-875 Guimar\u00e3es, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7326-4133","authenticated-orcid":false,"given":"Ana R.","family":"Freitas","sequence":"additional","affiliation":[{"name":"UCIBIO\u2014Applied Molecular Biosciences Unit, University Institute of Health Sciences (1H-TOXRUN, IUCS-CESPU), Avenida Central de Gandra 1317, 4585-116 Paredes, Portugal"},{"name":"UCIBIO\u2014Applied Molecular Biosciences Unit, Faculty of Pharmacy, University of Porto, Rua Jorge de Viterbo Ferreira 228, 4050-313 Porto, Portugal"},{"name":"Associate Laboratory i4HB, Institute for Health and Bioeconomy, Faculty of Pharmacy, University of Porto, Rua Jorge de Viterbo Ferreira 228, 4050-313 Porto, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1405-2277","authenticated-orcid":false,"given":"Nuno V.","family":"Brito","sequence":"additional","affiliation":[{"name":"UCIBIO\u2014Applied Molecular Biosciences Unit, University Institute of Health Sciences (1H-TOXRUN, IUCS-CESPU), Avenida Central de Gandra 1317, 4585-116 Paredes, Portugal"},{"name":"CISAS\u2014Center for Research and Development in Agrifood Systems and Sustainability, Polytechnic Institute of Viana do Castelo, NUTRIR (Technological Center of AgriFood Sustainability), Monte de Prado, 4960-320 Melga\u00e7o, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9640-9377","authenticated-orcid":false,"given":"Carla","family":"Miranda","sequence":"additional","affiliation":[{"name":"UCIBIO\u2014Applied Molecular Biosciences Unit, University Institute of Health Sciences (1H-TOXRUN, IUCS-CESPU), Avenida Central de Gandra 1317, 4585-116 Paredes, Portugal"},{"name":"LAQV-REQUIMTE\u2014Associated Laboratory for Green Chemistry, University NOVA of Lisbon, 1099-085 Caparica, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Almansour, A.M., Alhadlaq, M.A., Alzahrani, K.O., Mukhtar, L.E., Alharbi, A.L., and Alajel, S.M. 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